ioctl VIDIOC_G_OUTPUT, VIDIOC_S_OUTPUT &manvol; VIDIOC_G_OUTPUT VIDIOC_S_OUTPUT Query or select the current video output int ioctl int fd int request int *argp fd &fd; request VIDIOC_G_OUTPUT, VIDIOC_S_OUTPUT argp To query the current video output applications call the VIDIOC_G_OUTPUT ioctl with a pointer to an integer where the driver stores the number of the output, as in the &v4l2-output; index field. This ioctl will fail only when there are no video outputs, returning the &EINVAL;. To select a video output applications store the number of the desired output in an integer and call the VIDIOC_S_OUTPUT ioctl with a pointer to this integer. Side effects are possible. For example outputs may support different video standards, so the driver may implicitly switch the current standard. It is good practice to select an output before querying or negotiating any other parameters. Information about video outputs is available using the &VIDIOC-ENUMOUTPUT; ioctl. &return-value; EINVAL The number of the video output is out of bounds, or there are no video outputs at all.